Computer systems frequently include a number of circuit packs which are directly coupled to a shared bus. Each circuit pack interfaces to the bus via one or more devices, which, depending on the functions to be performed on that circuit pack, may be transmitters, receivers or transceivers. If one of the devices fails due to a shorted semiconductor junction, for example, the bus or a portion thereof can become locked at either logic zero or logic one due to the resulting low impedance path to the voltage source used to energize the circuit pack. Although detecting a bus fault of this type is relatively easy, isolating the failure to a particular circuit pack is more difficult, frequently being done by manually replacing one circuit pack at a time. The present invention is a method and apparatus for automatically locating the source of such bus faults.